"""FreeRouting JAR oracle for behaviour-level validation.

**Dev/test only — not part of the shipped package** (freeroute is Java-free by
design). This runs the reference FreeRouting JAR to route a Specctra DSN so that
freeroute's own output can be diffed against the reference implementation. There
are no unit-test oracles for FreeRouting's geometry/router, so the oracle is how
we validate at the behaviour level: same DSN in, compare routed connectivity.

Tests that use this skip automatically when a Java 21+ runtime or the JAR is not
available (e.g. CI without a JVM), so the normal suite stays Java-free.

Overrides:
- ``FREEROUTE_ORACLE_JAVA`` — explicit path to a ``java`` binary.
- ``FREEROUTING_JAR`` — explicit path to a freerouting JAR.
"""

from __future__ import annotations

import contextlib
import glob
import os
from pathlib import Path
import re
import shutil
import subprocess
import tempfile

import pytest

from freeroute.dsn.sexp import parse

_MIN_JAVA_MAJOR = 21
_REPO_ROOT = Path(__file__).resolve().parents[1]

# JARs bundled in the (gitignored) reference clone, newest first.
_JAR_CANDIDATES = (
    "reference/freerouting/scripts/benchmark/binaries/freerouting-current.jar",
    "reference/freerouting/scripts/benchmark/binaries/freerouting-2.2.4.jar",
    "reference/freerouting/integrations/KiCad/kicad-freerouting/plugins/jar/freerouting-2.2.4.jar",
    "reference/freerouting/scripts/benchmark/binaries/freerouting-1.9.0.jar",
)


def _java_major(java: str) -> int:
    """Parse the major version from ``java -version`` (handles the old 1.8 form)."""
    try:
        out = subprocess.run(
            [java, "-version"], capture_output=True, text=True, timeout=10
        ).stderr
    except (OSError, subprocess.SubprocessError):
        return 0
    m = re.search(r'version "(\d+)(?:\.(\d+))?', out)
    if not m:
        return 0
    major = int(m.group(1))
    # "1.8.0" -> 8; "26.0.1" -> 26
    return int(m.group(2)) if major == 1 and m.group(2) else major


def find_java() -> str | None:
    """Return a path to a Java >= 21 runtime, or None."""
    candidates: list[str] = []
    override = os.environ.get("FREEROUTE_ORACLE_JAVA")
    if override:
        candidates.append(override)
    java_home = os.environ.get("JAVA_HOME")
    if java_home:
        candidates.append(os.path.join(java_home, "bin", "java"))
    # Arch-style versioned JVMs, newest major first.
    candidates += sorted(
        glob.glob("/usr/lib/jvm/java-*-openjdk/bin/java"), reverse=True
    )
    on_path = shutil.which("java")
    if on_path:
        candidates.append(on_path)

    for java in candidates:
        if java and os.path.isfile(java) and _java_major(java) >= _MIN_JAVA_MAJOR:
            return java
    return None


def find_freerouting_jar() -> str | None:
    """Return a path to a runnable freerouting JAR, or None."""
    override = os.environ.get("FREEROUTING_JAR")
    if override and os.path.isfile(override):
        return override
    for rel in _JAR_CANDIDATES:
        p = _REPO_ROOT / rel
        if p.is_file():
            return str(p)
    return None


JAVA = find_java()
JAR = find_freerouting_jar()
HAS_ORACLE = JAVA is not None and JAR is not None

requires_oracle = pytest.mark.skipif(
    not HAS_ORACLE, reason="FreeRouting oracle unavailable (needs Java 21+ and a freerouting JAR)"
)


def route_dsn(dsn_path: str | Path, *, max_passes: int = 6, timeout: int = 180) -> str:
    """Route ``dsn_path`` with the FreeRouting JAR and return the SES text.

    Raises RuntimeError if the oracle is unavailable or produced no SES.
    """
    if not HAS_ORACLE:
        raise RuntimeError("FreeRouting oracle unavailable")
    with tempfile.NamedTemporaryFile(suffix=".ses", delete=False) as tmp:
        out_path = tmp.name
    try:
        subprocess.run(
            [JAVA, "-jar", JAR, "-de", str(dsn_path), "-do", out_path, "-mp", str(max_passes)],
            capture_output=True,
            text=True,
            timeout=timeout,
            check=False,
        )
        text = Path(out_path).read_text()
    finally:
        with contextlib.suppress(OSError):
            os.unlink(out_path)
    if not text.strip():
        raise RuntimeError("FreeRouting produced an empty SES")
    return text


def routed_nets(ses_text: str) -> dict[str, dict[str, int]]:
    """Map each net in an SES ``network_out`` to its wire/via counts.

    This is the diff primitive the router phase compares against: two SES files
    route the "same" board when they cover the same set of nets with wires/vias.
    """
    root = parse(ses_text)
    routes = root.child("routes")
    if routes is None:
        return {}
    network_out = routes.child("network_out")
    if network_out is None:
        return {}
    result: dict[str, dict[str, int]] = {}
    for net in network_out.children("net"):
        vals = net.values()
        name = vals[0].text if vals else "?"
        result[name] = {
            "wires": len(net.children("wire")),
            "vias": len(net.children("via")),
        }
    return result


def routed_net_set(ses_text: str) -> set[str]:
    """Return the set of nets that actually carry routing (>=1 wire or via)."""
    return {
        name
        for name, counts in routed_nets(ses_text).items()
        if counts["wires"] or counts["vias"]
    }